Assulina Muscorum Research Articles

Hydroclimate Changes Based on Testate Amoebae in the Greater Khingan Mountains’ Peatland (NE China) during the Last Millennium

The driving force of climate change in the monsoon margin is complex, making it a key area for regional and global climate change research. Palaeohydrological studies in the monsoon margin have increased the resolution of research in the long term, transitioning from qualitative to quantitative studies to comprehend climate change processes, patterns, and mechanisms. Testate amoebae (TA) in peat sediments are used as a proxy indicator organism for quantitative reconstruction of palaeohydrology. Thus, their community changes are directly related to precipitation, and widely used to reconstruct the patterns of summer precipitation globally. We investigated TA species and reconstructed palaeohydrological changes in the Greater Khingan Mountains’ Hongtu (HT) peatland, located in the East Asian Summer Monsoon (EASM) margin. The result showed that the most abundant TA species were Assulina muscorum (12.4 ± 5.0%) and Nebela tincta (8.9 ± 4.9%) in the HT peat core. The increase in dry indicator species (e.g., A. muscorum and Alabasta militaris) indicated a drying pattern in the HT peatland since 150 cal yr BP. Principal component analysis (PCA) explained 47.6% of the variation in the selected TA assemblages. During 400 to 250 cal yr BP, PCA axis 1 scores ranged from 0.2 to −1.3 (reflecting a drier climate), associating with the Little Ice Age. The paleohydrology of the northern part of the Greater Khingan Mountains was mainly controlled by the EASM, which was associated with changes in North Atlantic Sea surface temperature and solar radiative forcing. The apparent drying pattern may be the result of the gradual intensification of anthropogenic activities and the increase in EASM intensity.

Distribution of testate amoebae in bryophyte communities in São Miguel Island (Azores Archipelago).

BackgroundTestate amoebae are a polyphyletic group of protists living preferentially in soils, freshwaters and wetlands. These Protozoa have a worldwide distribution, but their presence and diversity in the Azores (a remote oceanic archipelago) is poorly known, with only twelve taxa recorded so far. The published information reflects occasional collections from sporadic field visits from naturalists to São Miguel Island, mainly in the nineteenth century. To overcome this limitation, a standardised survey was carried out on the Island, sampling different types of habitats from several localities to provide the distribution and information on species ecology of testate amoebae.New informationIn this study, 43 species of testate amoebae were recorded (within a total of 499 occurrences), belonging to two orders of Protista (26 Arcellinida and 17 Euglyphida). The most frequently occurring testate amoebae were Euglypha strigosa, Trinema lineare, Euglypha rotunda, Assulina muscorum and Cyclopyxis eurystoma. The most diverse genus was Euglypha (six species). A total of 38 species are new records for the Azores Archipelago. These data help to improve knowledge of the geographical distribution of testate amoebae in the northern hemisphere and their diversity in the Azores Archipelago.

Testate amoebae as a hydrological proxy for reconstructing water-table depth in the mires of south-eastern Australia

Although it is well established that moisture availability in south-eastern Australia has been decreasing through time recently, the driver(s) of this trend are contentious, and our understanding of any drivers is limited by a relatively short historic record. Testate amoebae have been widely used to reconstruct peatland hydrology in the Northern Hemisphere, but in the Southern Hemisphere research is still needed to assess their proficiency as a palaeohydrological proxy and to develop robust transfer functions. Here we examine the ecology of testate amoebae in several high altitude mires in south-eastern Australia and present the first transfer function for the continent. Euglypha tuberculata type, Centropyxis platystoma type and Assulina muscorum were the most common taxa in our modern samples. Water-table depth was the primary environmental variable determining testate amoebae assemblages and therefore transfer functions were developed for this ecological factor. We found that the performance of various all-species and species-pruned transfer functions were statistically robust, with R2 values of around 0.8 and Root Mean Squared Error of Prediction (RMSEP) values of about 7 cm. All cross-validation methods (leave-one-out RMSEP, cluster-bootstrap RMSEP, segment-wise RMSEP and leave-one-site-out RMSEP from all-species and species-pruned transfer functions) suggested that the Modern Analogue Technique (MAT) was the best performing transfer function, with negligible bias evident from un-even sampling and spatial autocorrelation. We also used a new approach to evaluate the importance of taxa and the performance of our transfer functions using species-pruned methods. Our results suggest that the all-species MAT, with an RMSEP of 5.73 and R2 of 0.86, provides the best reconstruction of water-table depth across our sites in south-eastern Australia.

Mikrofosylia pozapyłkowe w torfach Polesia Lubelskiego i ich wartość wskaźnikowa

<p>Artykuł stanowi pierwsze opracowanie typów mikrofosyliów pozapyłkowych (ang. non-pollen palynomorphs; NPP) występujących w próbkach palinologicznych z torfowisk Polesia Lubelskiego i stanowiących istotne bioindykatory zmian paleohydrologicznych w holocenie. Analizie na obecność NPP poddano torfy z trzech stanowisk: Płotycze, Mytycze i Durne Bagno. Oznaczono kilkanaście typów NPP wśród których występowały mikrofosylia pochodzenia zwierzęcego i grzybowego. Te same typy mikrofosyliów pozapyłkowych są powszechnie w torfowiskach Niżu Europejskiego. Większość z nich stanowią bowiem gatunki kosmopolityczne. Zidentyfikowane NPP w torfach Polesia Lubelskiego są zgodne z opisami zawartymi w międzynarodowych kluczach do oznaczania. </p>

Late-Holocene climate dynamics recorded in the peat bogs of Tierra del Fuego, South America

The ombrotrophic peat bogs of Tierra del Fuego are located within the southern westerly wind belt (SWWB), which dominates climate variability in this region. We have reconstructed late-Holocene water-table depths from three peat bogs and aimed to relate these records to shifts in regional climate. Water-table depths were quantified by the analysis of testate amoeba assemblages, and a regional transfer function was used to infer past water-table depths. During the last 2000 years, testate amoeba assemblages have been relatively stable, with a dominance of Difflugia pulex and Difflugia pristis type, and an increase in Assulina muscorum and other Euglyphida at the top of each section. Multivariate analyses show that water-table depth remained the main environmental variable explaining assemblages along the TiA12 core, but reconstructions were not significant for the two other cores. In line with the low variability in assemblages, water tables were relatively stable during the last 2000 years. Slightly wetter conditions were found between ~1400 and 900 cal. BP and a pronounced recent dry shift was reconstructed in all of the three peat profiles. Considering the regional climatic context, this recent shift may have been forced by a decrease in precipitation and warmer conditions linked to an increase in the importance of the SWWB. Nevertheless, we cannot exclude the influence of higher UV-B radiation resulting from the local degradation of the ozone layer since the late 1970s, which may have had an additional effect on the relative presence of A. muscorum in the southern Patagonian region.

Distribution of soil-inhabiting testate amoebae along a mountain slope (Baikal Lake region, Khamar-Daban ridge, Cherskii peak)

The specific composition and distribution of soil-inhabiting testate amoebae along the Cherskii peak slope (Khamar-Daban mountain ridge, Lake Baikal region) were studied within the altitude range from 1000 to 1570 m above sea level according to the changes in biogeocenoses from birch-aspen to cedar-fir forests to cedar-fir-bush forest-tundra. One-hundred-four taxa were identified. The most common species are ubiquits with a wide geographical distribution: Trinema lineare, Euglypha levis, Euglypha rotunda, Trinema enchelys, Phryganella acropodia, Tracheleuglypha dentata, Assulina muscorum, Trinema complanatum, and Centropyxis aerophila. The species richness varies from 12 to 40 species per sample, and the abundance varies from 500 to 120000 ind. per gram of absolutely dry soil. The spatial heterogeneity of the specific composition grows with altitude, and the community composition changes. The absence of a common pattern in the cenotic changes in the communities of testate amoebae in Western Europe and the Lake Baikal region is discussed.

Moss-dwelling testate amoebae and their community in Dajiuhu peatland of Shennongjia Mountains, China

Testate amoebae from a large fen peatland of China were investigated in August 2009. Thirty-six testate amoebae species belonging to 16 genera and one rotifer were identified. Three relatively drier indicator species, Assulina muscorum, Assulina seminulum, and Trinema-corythion type, were the dominate species, comprising 54% of total amoebae shells. Non-metric multidimensional scaling (NMS) ordination divided the testate amoebae assemblages into two groups – a drier group including A. muscorum, A. seminulum, Euglypha rotunda type, Trinema-corythion type, and Plagiopyxis callida and a wetter group including Centropysis cassis, Cyphoderia ampulla, Difflugia oblonga, Difflugia lanceolata, Euglypha strigosa type, Nebela galeata, Nebela lageniformis, and Quadruella symmetrica. Pearson correlations showed that most testate amoebae species between the two groups are negatively correlated, reflecting the possible influence of a moisture gradient. However, the ubiquitous distributions of other testate amoebae in the two-dimensional NMS ordination map suggested that factors other than moisture are also influencing the testate amoebae community in the fen.

COI gene and ecological data suggest size-dependent high dispersal and low intra-specific diversity in free-living terrestrial protists (Euglyphida: Assulina)

Aim Propagule size and ecological requirements are believed to be major factors influencing the passive dispersal of free-living terrestrial protists. We compared the colonization potential of three closely related testate amoeba species (Assulina muscorum, A. seminulum, A. scandinavica, ranging from 40 to 100 μm in length). Location Europe. Methods We collected individual Assulina species cells from Sphagnum peatlands across Europe. We sequenced a 550-bp fragment of the mitochondrial cytochrome c oxidase subunit I gene (COI) to estimate the within-species variability, as a proxy for gene flow. We reviewed existing ecological and palaeoecological data to assess the ecological tolerance of Assulina species and how rapidly they colonized developing peatlands. Results We obtained COI sequences for 30 individuals of A. seminulum from eleven sites, for 39 of A. muscorum from six sites, and for six of A. scandinavica from two sites. We observed three haplotypes for A. seminulum and two for A. muscorum, often co-existing in the same sites. The sequences of A. scandinavica from the two sites were identical. Assulina muscorum and A. seminulum haplotypes varied by only 1–2 nucleotides, resulting in >99.5% similarity. Genetic diversity within A. seminulum was higher than that within A. muscorum. Ecological and palaeoecological records showed that A. muscorum was much more frequent and abundant than A. seminulum, and had a somewhat broader ecological tolerance for pH, moisture and water-table depth. Assulina muscorum always appeared early during the developmental history of peatlands, either before or simultaneously with A. seminulum. Main conclusions The lack of genetic structure observed with a variable marker such as COI suggests high gene flow between the sites and thus rapid transport (at an evolutionary scale) over large distances, in agreement with the palaeoecological records. Thus, geographical distance alone does not seem to prevent the dispersal of testate amoebae, at least within Europe. Nevertheless, genetic diversity was significantly lower within A. muscorum than within A. seminulum, suggesting that its smaller size and abundance and/or broader ecological tolerance influence its effective dispersal capacity. These results are in agreement with the often earlier colonization of peatlands by A. muscorum and its broader ecological tolerance.

The curse of taxonomic uncertainty in biogeographical studies of free‐living terrestrial protists: a case study of testate amoebae from Amsterdam Island

AbstractAim A current debate in microbial biogeography contrasts two views concerning the distribution of free‐living microorganisms. The first view assumes a ubiquitous distribution, while the second assumes that at least some species have limited geographical distributions. We tested for limited geographical distributions by identifying testate amoebae morphospecies from an extremely remote oceanic island where the potential for endemism is high.Location Amsterdam Island, Indian Ocean.Methods Sixty moss and water samples collected from the top of the volcano to the lowland were investigated for their testate amoeba content. Due to taxonomic uncertainties among the Argynnia (Nebela) dentistoma species complex (including A. antarctica), we also performed light and scanning electron microscopy investigations on the shell ultrastructure and biometric analyses on several specimens of this taxon.Results We identified a total of 43 testate amoeba taxa belonging to 15 genera. Only four testate amoeba taxa had previously been recorded on this island. Testate amoeba communities of Amsterdam Island are dominated by cosmopolitan ubiquitous euglyphid taxa such as Trinema lineare, Assulina muscorum and Corythion dubium. The length and width ranges for Argynnia dentistoma on Amsterdam Island overlap with other records of this species and of A. antarctica, suggesting that A. antarctica is not a distinct taxon.Main conclusions Although Amsterdam Island is among the most remote islands in the world, an extensive inventory of testate amoeba morphospecies provided no clear evidence for endemism. On the one hand, our detailed morphometric analysis of the A. dentistoma complex revealed that A. antarctica, a morphospecies previously suggested to display endemism, cannot be confidently distinguished from the cosmopolitan morphospecies A. dentistoma. On the other hand, five morphotaxa could not be identified with certainty and might represent new species, potentially with limited distribution. These examples illustrate how taxonomic uncertainties undermine biogeographical studies of testate amoebae. In order to allow better interpretation of morphology‐based testate amoeba distribution data, an assessment of genetic diversity among and within morphotaxa in relation to geographical distance for some common testate amoebae should be given high priority.

Examining the dissolution characteristics of testate amoebae (Protozoa: Rhizopoda) in low pH conditions: Implications for peatland palaeoclimate studies

A laboratory-based experiment was carried out to examine the dissolution characteristics of testate amoebae (Protozoa: Rhizopoda) under acidic conditions. The results suggest a large degree of variability in the dissolution susceptibility of taxa and no straightforward distinction between the relative robustness of xenosomic and idiosomic test types. Individuals from the genus Euglypha have tests composed of thin-walled siliceous plates, which are prone to severe dissolution. Certain other taxa are relatively unaffected by low pH conditions, including Assulina muscorum, Amphitrema flavum and Trigonopyxis arcula type. Differential preservation of subfossil testate amoebae must be acknowledged as a particular problem for peat-based palaeoclimate studies.

Vertical micro-distribution and response to nitrogen deposition of testate amoebae in Sphagnum.

Previous studies have shown the existence of a vertical micro-distribution of testate amoebae in the first centimeters of Sphagnum and their response to nutrient enrichment. In order to test the response of testate amoebae to depth and N addition in dry moss carpets recolonizing cutover peatlands, we sampled Sphagnum that had received 0, 1, 3, or 10g N m(-2) yr(-1) for three years. The mosses were cut into three segments: 0-1cm, 1-3cm and 3-5cm and analyzed for testate amoebae. The overall diversity (22 taxa) was high considering the dryness of the site, but the species richness of individual samples was low (mean 6.6). The presence of several species characteristic of wetter conditions suggests that they have a broader tolerance than usually believed and/or have a high colonization potential. Species richness increased with depth. Assulina muscorum was most abundant in the top segment, while Phryganella acropodia, Heleopera rosea and Nebela militaris were most abundant in the deepest segment. Neither the metabolism type nor the shell characteristics significantly explained the vertical distribution of species. There was no overall response of testate amoebae to N, although one species, Bullinularia indica, was significantly more abundant in the fertilized than in the control plots.

Response of Testate Amoebae (Protozoa) to N and P Fertilization in an Arctic Wet Sedge Tundra

There are few data on the effect of long-term manipulations on soil protozoa, and almost nothing is known about soil protozoa in Alaska. I studied the response of testate amoebae to nitrogen and phosphorus addition in an Arctic fen, at Toolik Lake Long-Term Experimental Research (LTER) Station, Alaska. Testate amoebae were extracted from Sphagnum mosses in control and fertilized plots. Of the 35 testate amoebae taxa recorded, 7 are first observations for the Arctic (excluding Russia) and 14 for Alaska. The total density and biomass of testate amoebae were significantly reduced, by 77% and 84%, in the fertilized plots. The structure of testate amoebae communities was also modified in those plots, although for most taxa the changes were not significant. Four taxa (Amphitrema flavum, Assulina muscorum, Placocista spinosa ssp. hyalina, and Hyalosphenia papilio) accounted for over half of the population in the control plots but only for 11% in the N and P plots. The densities of A. muscorum and Difflugia oviformis were significantly lower in the N and P–treated plots. The relative abundance and contribution to biomass of Centropyxis aerophila, Phryganella acropodia, and Tracheleuglypha dentata increased in the fertilized plots, while that of D. oviformis decreased. These effects suggest that testate amoebae respond to nutrient manipulations in the Arctic.

Some information on testate amoebae of Iceland

In samples of mosses collected during an expedition in the year 1987 along the southern border of Iceland, in seven habitats on the slopes of Skerhöll Hill, south of the glacier Svínafellsjökull, 80 taxa of testate amoebae have been recorded. From these taxa 24 species are new to Iceland. Up to now, including our own data, on the basis of available sources 174 taxa have been reported for Iceland. In the mosses Racomitrium heterostichum and Racomitrium fasciculare an Assulina muscorum — Centropyxis globulosa-association has been recorded.

Effects of caffeine treatment on the fine structure, silica secretion, and shell morphology of the testate amoeba Assulina muscorum

Assulina muscorum secretes morphologically altered shells when cultured in a medium with 5 mM caffeine. The siliceous scales, normally distributed in a regular overlapping pattern, are disorganized, thicker and wider than normal, and occasionally have incompletely silicified surfaces that appear irregular in profile in transmission electron microscopic ultrathin sections. The shape of the silica deposition vesicles (SDVs) in the cytoplasm is altered and they are less regularly arranged. The swollen appearances of the SDVs, and of nearby Golgi tubules, give additional evidence that caffeine affects the fine structural morphology of membranous secretory organelles and can disrupt their normal depositional activity. In addition to the greater thickness and width of the siliceous scales in caffeine-treated cells, the length and width of the shell are larger compared to controls, but the aspect ratio (length / width) is smaller. The latter is attributed to a larger increase in width relative to the increase in length of the caffeine-reated cells. Since some of the scales are deposited with the long axis laterally on the shell surface, in addition to being greater in width, this raises the interesting question of whether the morphology of the SDVs and the siliceous products influences the size and morphogenesis of the shell. Further research is needed to clarify the interaction of the SDVs with the cytoplasmic cytoskeletal system during shell morphogenesis. © 1995 Wiley-Liss, Inc.

The fine structure of the euglyphid testate amoeba Assulina muscorum (Rhizopoda: Euglyphidae) with observations of growth rate in culture, morphometries, and siliceous scale deposition

Summary Scanning and transmission electron microscopic analysis of the shell and cytoplasm of Assulina muscorum Greef, 1888 show that the siliceous scales of the test are characteristic of other euglyphid species and originate in the posterior portion of the cytoplasm near Golgi bodies. The scales are deposited within vesicles, mature as they move anteriorly, and become stored within enclosing vesicles in the vicinity of pigment granules. A frothy layer of vacuolated cytoplasm, containing digestive vacuoles with bacteria, extends anteriorly toward the aperture, and occasionally includes small amoebae (c. 2–3 μm) that appear to be commensals. Reserve bodies, possibly lipid, are more abundant in the posterior cytoplasm surrounding the nucleus. The nucleus varies in shape from approximately circular in sections to elongate or lobate and contains a centrally located nucleolus. In overall view, the fine structure of A. muscorum resembles similar terrestrial euglyphid species such as Tracbeleuglypha dentata . Membrane-bound, electron-opaque granules with less dense cylindrical cores may be secretory granules, and appear to be different from those reported in other euglyphid species. The doubling time in laboratory culture is 3.8 to 4.3 days, and the natural growth coefficient is 0.19 to 0.17 depending on the kind of growth medium.

Holocene changes on a peatland in northwestern Ontario interpreted from testate amoebae (Protozoa) analysis

Radiocarbon‐dating and analyses of fossil testate amoebae (Protozoa) have established changes in soil moisture conditions on the developing surface of a Sphagnum ‐dominated peatland near Emo in northwestern Ontario.The distribution and composition of modern testate amoebae communities were studied from peatlands in the region of Ontario and Minnesota as a guide to interpreting fossil assemblages. Although the core spans all of the Holocene, fossil testate amoebae were recovered only from the part post‐dating 6500 BP. Earliest testate amoebae assemblages associated with bryophytic and cyperaceous‐rich fen peat are dominated by species in the genera Cyclopyxis and Centropyxis. By 5000 BP, Amphitrema Jraaum, Assulina muscorum, Heleopera sphugni and Hyalosphenia subjaoa become important species as Sphagnum‐rich peat accumulated at the site. Present‐day microtopographic differentiation probably developed during historic time when the site became progressively drier, as indicated by a change of Nebela griseola, N. militaris and Trigonopyxis arcula. Although it is possible to derive quantitative estimates of changing soil moisture conditions from testate amoebae, care should be taken in interpreting results, particularly from non‐Sphagnum‐rich peats, until more is learned about the distribution and ecology of modern faunas.

On the Habitat Specificity of the Testate Amoebae Assemblages from Devon Island (NWT, Canadian Arctic), with the Description of a New Species: Difflugia ovalisina

Summary A classification analysis of samples from different habitats demonstrates the importance of some ubiquistic and cosmopolitic taxa in high arctic environments. The number of habitat specific assemblages was found to be rather low: only 6 out of 18 recognized assemblages could be linked to a specific habitat. These assemblages are: for the soils, the Plagiopyxis callida assemblage; for the moss habitats, the Assulina muscorum — Corythion dubium , and the Euglypha rotunda assemblages; for the aquatic habitats, the Trinema lineare and the Paraquadrula irregularis — P. penardi assemblages. A new species, Difflugia ovalisina , is described.

The Testate Amoebae from the Søndre Strømfjord Region (West-Greenland) Their Biogeographic Implications

A survey of the testate amoebae fauna of the inland area near Søndre Strømfjord (West Greenland) revealed 79 taxa belonging to genera. Dry moss habitats are characterized by the Assulina muscorum and Corythion dubium assemblages, while the Arcella rotundata assemblage is found in the wettest ones. The mcsotrophic-eutrophic waters bear a Difflugia gramen assemblage, while the Trinema lineare assemblage is one of those living in oligotrophic waters. In soils, the content of organic material and perhaps of CaCO3 differentiate the Plagiopyxis, the Centropyxis aerophila - Centropyxis minuta and the Centropyxis aerophila - Phryganella acropodia assemblages. An evaluation of the composition of the fauna, based on the importance of the genus Centropyxis and the poor representation of Difflugia in the waters, the occurrence of taxa so far only known from the Arctic, and the presence of the arctic-alpine Centropyxis pontigulasiformis, indicates a rather low-arctic biogeographic position tor the studied region.

Testate Amoebae (Protozoa) as Indicators of Drainage in a Forested Mire, Northern Ontario, Canada

Summary Testate amoebae (Protozoa) were examined in a Picea mariana forested mire in northern Ontario, Canada to assess the use of testate amoebae as environmental bioindicators of drainage. Habitat types included Picea mariana trees, Ericaceae shrubs, and Sphagnum mosses. Several of the species or species groups recorded in the study area, emerged as showing significant differences in abundance between control and drained microsites. Significant differences were recorded between control and drained microsites for Cyclopyxis arcelloides-type Assulina muscorum and Centropyxis aerophila-type in certain site types. In other site types Cyclopyxis arcelloides, Trinema lineare, and Centropyxis aerophila-type, decreased in abundance with drainage whereas Assulina muscorum and Corythion dubium increased in abundance with drainage. This study demonstrates for the first time that alterations in the soil microenvironment from drainage are reflected almost immediately by the abundance of certain species of testate amoebae, some of which increase in number, whereas other decrease in number. Testate amoebae may, therefore, be used to monitor environmental effects of drainage in peatland forestry.

Evolutionary studies on the Assulina-Valkanovia complex (Rhizopoda, Testaceafilosia) in Sphagnum and soil

The taxonomy and evolution of the Assulina-Valkanovia complex were investigated in a spruce forest soil which included a Sphagnum plot (GDR, Thuringia). In both habitats Assulina muscorum occurred in two colour forms (brown and colourless) and four shapes. A quantified phenospectrum from Assulina muscorum was obtained. The four shapes were distributed differently between the brown and the colourless forms in Sphagnum and soil. The shell measurements showed statistically significant differences between the brown and the colourless forms. Even between the two brown populations there were some significant differences. Each of the four shape types of brown and of colourless Assulina can be kept in clonal cultures for some time. However, without selection, single cultures eventually revert to mixed types. The four shape types show different degrees of stability. These colour and shape forms are genotypes, which can also occur for short periods in the natural habitats. The brown populations in Sphagnum and in the soil were dominated by different shape types during the period of investigation. Valkanovia elegans cannot be distinguished from Assulina muscorum type 4, but Valkanovia can inhabit both upper and lower soil horizons, whereas Assulina and its forms lives exclusively in the upper horizon (litter). Valkanovia from the lower horizon is constant in clonal culture. The conclusion of the present investigation is that there are stable and unstable constellations within a changeable genome, which give asexual groups both a taxonomic structure and a continuum of forms. Selection can increase stability, by polygenic control of features.